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WASAVIES: Warning System for Aviation
Exposure to Solar Energetic Particles Tatsuhiko Sato (JAEA), Ryuho Kataoka (NIPR),
Yûki Kubo (NICT), Daikou Shiota (STEL), Seiji Yashiro (CUA),
Takao Kuwabara (Delaware Univ.), and Hiroshi Yasuda (NIRS)
1
Space Weather Workshop 2014 @ Boulder CO on 8-11 April 2014
This work has been submitted for publication in Space Weather
Table of contents
• Background of WASAVIES
• Development of WASAVIES
• 3. Interplanetary SEP transport (Kubo)
• 4. Magnetospheric SEP trace (Kataoka)
• 5. Air-shower simulation (Sato)
• Preliminary Results of WASAVIES
• Summary and Future
2
Aircrew exposure by SEP and GCR
4
The Sun
Motion of cosmic-ray
in the Atmosphere
Ground
SEP GCR
m
EM
Cascade
Neutron
p
Proton
Ra
dia
tion
Le
vel
Hig
h
Lo
w
Accelerated by solar
flare and CME
Interplanetary Focused transport
Upper Atmosphere Cause nuclear interaction and generate air shower
Flight Altitude Deposit energies into human body
Galaxy Accelerated by
supernova remnants
Heliosphere Modulated by solar wind
Galactic Cosmic-Ray Solar Energetic Particle
Geomagnetic Field Change direction, reflected / penetrate
Continuously &
Low dose rates
Suddenly &
High dose rates
Geomagnetic
Field
Secondary particles Afterward Evaluation Forecast
Annual doses for aircrews
5
Yasuda, Isotope News (2009)
Average (mSv) Maximum (mSv)
Pilot 1.68 3.79
Cabin Attendant 2.15 4.24
Annual doses in 2007 for each pilot and cabin attendant
employed by Japanese airline companies
Annual dose limitation for aircrews in Japan is 5 mSv
Aircrew doses may exceed their limitation
Dose per flight during the largest solar particle event can exceed a few mSv …
Table of contents
• Background of WASAVIES
• Development of WASAVIES
• 3. Interplanetary SEP transport (Kubo)
• 4. Magnetospheric SEP trace (Kataoka)
• 5. Air-shower simulation (Sato)
• Preliminary Results of WASAVIES
• Summary and Future
6
Outline of WASAVIES
1. Detect ground level enhancement (GLE) onset by
multiple ground-based neutron monitor
2. Determine CME parameters such as its speed to predict
the CME driven SEP profile
3. Calculate time-varying shock accelerated SEP spectrum
4. Calculate SEP fluxes at the top of the atmosphere at
any latitude & longitude using proton trace model
5. Calculate secondary particle fluxes in the atmosphere
using database developed based on air shower
simulation
6. Convert their fluxes on flight routes to corresponding
doses using dose-conversion coefficients
7
1. Detect ground level enhancement (GLE) onset by
multiple ground-based neutron monitor
2. Determine the mean free path (MFP) of SEP on the
basis of solar wind simulation
3. Determine SEP flux outside the magnetosphere using
the MFP and focused transport simulation
Aim to forecast SEP doses within 2.5 hours after flare onset
1
2
3
4 5&6
10 15
103
104
105
Time (h)
Incr
ease
Count
Rate
(100cp
h)
Exp.
Cal. (Matthia)
Cal. (This work)
Forward models of WASAVIES
1&2. GLE alarm & Solar wind 3. Interplanetary SEP Transport
4. Magnetospheric SEP trace 5. Air-shower (Sato+ 2013)
Parker spiral
Mean free path
Injection spectra
Energy spectra
(normalized)
Energy spectra at
top of atmosphere
GLE Alarm
(Kuwabara+ 2006)
Solar wind simulation
(Shiota+ 2014)
8
Table of contents
• Background of WASAVIES
• Development of WASAVIES
• 3. Interplanetary SEP transport (Kubo)
• 4. Magnetospheric SEP trace (Kataoka)
• 5. Air-shower simulation (Sato)
• Preliminary Results of WASAVIES
• Summary and Future
9
3. Formulation of SEP transport
10 National Institute of Information and Communications Technology
1-D (spatial) focused transport equation (FTE) with adiabatic deceleration
𝜕𝑓
𝜕𝑡+ 𝜇𝑣𝑏𝑖𝜕𝑖𝑓 + 𝑉𝑖𝜕𝑖𝑓 +
𝑑𝑝
𝑑𝑡
𝜕𝑓
𝜕𝑝+𝑑𝜇
𝑑𝑡
𝜕𝑓
𝜕𝜇−
𝜕
𝜕𝜇𝐷𝜇𝜇
𝜕𝑓
𝜕𝜇= 0
Momentum change 𝑑𝑝
𝑑𝑡= 𝑝
1−3𝜇2
2𝑏𝑖𝑏𝑗𝜕𝑖𝑉𝑗 −
1−𝜇2
2𝜕𝑖𝑉𝑖 ←Adiabatic deceleration by solar wind divergence
Pitch angle change 𝑑𝜇
𝑑𝑡=1 − 𝜇2
2−𝑣𝑏𝑖𝜕𝑖 ln 𝐵 + 𝜇 𝜕𝑖𝑉𝑖 − 3𝑏𝑖𝑏𝑗𝜕𝑖𝑉𝑗
Pitch angle scattering coefficient: Modified quasi-linear theory (Beeck & Wibberenz 1986, Bieber+1994)
𝐷𝜇𝜇 = 𝐷0𝑣𝑅𝑞−2 𝜇 𝑞−1 + ℎ 1 − 𝜇2 q: Index of wave number spectrum of solar wind turbulence
Mean free path
𝜆∥ =3𝑣
8
(1−𝜇2)2
𝐷𝜇𝜇𝑑𝜇
1
−1 𝜆∥ cos
2𝜑 ≡ 𝜆𝑟 = const. (approx.)
Streaming ↓
↑ Convection
Momentum change ↓
↑ Pitch angle change
Pitch angle scattering ↓
↑ Adiabatic focusing
Solar wind divergence ↓
Modification to avoid no scattering at 𝝁 = 𝟎
3. Determine SEP flux and so on
11
Simulated intensity (top) and anisotropy (middle) of 100MeV SEP
at the Earth, and SEP injection profile near the Sun (bottom).
National Institute of Information and Communications Technology
Temporal evolution of pitch angle distribution
for 0.6 AU mean free path cases.
𝑓 𝑡 𝑑𝑡 =𝜇3
2𝜋𝜎2𝑡3exp −
𝜇 𝑡 − 𝜇 2
2𝜎2𝑡𝑑𝑡
Rigidity spectra evolution
3. Three types of injection profiles
12
80 MeV proton normalized differential flux → calibrated with GOES real-time observations
IP = 1 2 3
GOES: solid curve
IP = 1: The most impulsive profile of GLE69 event IP = 2: Five times longer time scale than that of GLE69 event IP = 3: Ten times longer time scale than that of GLE69 event
National Institute of Information and Communications Technology
Choose one of three profile by comparing 80 MeV GOES data and calculated flux
Table of contents
• Background of WASAVIES
• Development of WASAVIES
• 3. Interplanetary SEP transport (Kubo)
• 4. Magnetospheric SEP trace (Kataoka)
• 5. Air-shower simulation (Sato)
• Preliminary Results of WASAVIES
• Summary and Future
13
4. SEP transport in magnetosphere
Tyganenko89 (2005/1/20), N65 E00 80km, 1-100 GV p-
14
Negatively charged protons are traced back from the top of atmosphere
to outside of magnetosphere.
Table of contents
• Background of WASAVIES
• Development of WASAVIES
• 3. Interplanetary SEP transport (Kubo)
• 4. Magnetospheric SEP trace (Kataoka)
• 5. Air-shower simulation (Sato)
• Preliminary Results of WASAVIES
• Summary and Future
15
5. Air-shower simulation
16
10–8
10–4
100
104
0
0.0005
0.001
0.0015
0
0.5
1
1.5 d = 101 g/cm2 (~16.0 km)
rc = 0.7 GVsmin
Exp. (Goldhagen et al.)
Simulation
0
0.2
0.4
d = 201 g/cm2 (~11.8km)
rc = 4.3 GVsmin
Neutron Energy (MeV)
Neutr
on F
lux (
cm
–2s
–1le
tharg
y–1)
d = 1030 g/cm2 (ground level)
rc = 2.7 GVsmin
T. Sato et al. Radiat. Res. 166, 544 (2006), T. Sato et al. Radiat. Res. 170, 244 (2008)
Atmospheric Neutron fluxes
Reproduce the experimental data very much
Analyzed location (altitude & geomagnetic)
and time dependence of the fluxes
Proposed analytical model that can estimate
cosmic-ray fluxes anywhere and anytime in
the world** n, p, a, m+-, e-, e+, photon
Validity of the simulation procedure,
including the nuclear reaction models
Air-Shower Simulation
10–8
10–4
100
104
0
0.0005
0.001
0.0015
0
0.5
1
1.5 d = 101 g/cm2 (~16.0 km)
rc = 0.7 GVsmin
Exp. (Goldhagen et al.)
Simulation
PARMA
0
0.2
0.4
d = 201 g/cm2 (~11.8km)
rc = 4.3 GVsmin
Neutron Energy (MeV)
Neutr
on F
lux (
cm
–2s
–1le
tharg
y–1)
d = 1030 g/cm2 (ground level)
rc = 2.7 GVsmin
Exp.*
PHITS Simulation** Analytical Model
Analytical Model (EXPACS)
too time-consumptive …
*P. Goldhagen
Opened to public, http://phits.jaea.go.jp/expacs/
**Below 20 km & after AD1600 Excellent agreement can be observed
5. SEP dose estimation during GLE
17
0 500 100010
−4
10−2
100
102
104
Atmospheric depth (g/cm2)
Eff
ective d
ose (
uS
v/h
)
GCR (EXPACS*)
Total
Muon
Neutron
Electromagnetic
Proton
SEP
Total
Neutron dose is dominant at flight altitudes
Dose rates above McMurdo during the peak of the GLE
SEP Dose = ∫ SEP flux × Dose Conversion Coefficient
SEP ~ GCR
SEP ≫ GCR
* http://phits.jaea.go.jp/expacs/
Table of contents
• Background WASAVIES
• Development of WASAVIES
• 3. Interplanetary SEP transport (Kubo)
• 4. Magnetospheric SEP trace (Kataoka)
• 5. Air-shower simulation (Sato)
• Preliminary Results of WASAVIES
• Summary and Future
18
Table of contents
• Background WASAVIES
• Development of WASAVIES
• 3. Interplanetary SEP transport (Kubo)
• 4. Magnetospheric SEP trace (Kataoka)
• 5. Air-shower simulation (Sato)
• Preliminary Results of WASAVIES
• Summary and Future
21
Summary
• We have developed WASAVIES (Warning System for Aviation
Exposure to Solar Energetic Particles) to provide information to
aircrews.
• In present status, WASAVIES is composed of three simulations, SEP
transport in interplanetary space, SEP trace in magnetosphere, and
air-shower in atmosphere.
• WASAVIES can roughly reproduce dose rate with typical parameter of
spectrum index, mean free path, and solar wind speed, by only
changing the time-scale of SEP injection profiles at the Sun.
• It is interesting to note that such a simple setting creates the wide
varieties of GLEs.
22
Future
• WASAVIES gives the simplest start point, and a lot of improvements
are awaited.
– Use CME shock parameter to calculate SEP injection spectrum.
– Use solar wind simulation to reproduce interplanetary condition.
– Implement the system into JISCARD-EX for operational use.
– etc…
23
JISCARD-EX
24
Calculation of GCR doses
on the flight route
• Departure & arrival airports
• Date of the flight
Flight conditions Estimation of Flight Route
Vertical cut-off rigidity MAGNETOCOSMICS*
EXPACS
• Terrestrial cosmic-ray flux
• Dose conversion coefficients
• Force field potential (NM data**)
• Latitude & longitude
• Flight altitude & duration
Dose during the whole flight
* http://cosray.unibe.ch/~laurent/magnetocosmics/ ** http://neutronm.bartol.udel.edu/
Route-dose calculated by JISCARD-EX
0 5 100
2
4
Time (hour)
Eff
ective d
ose (
mS
v/h
)
Tokyo−Sydney (18 mSv)
Tokyo−Sanfrancisco (35 mSv)
Japanese Internet System for Calculating Route Dose
http://www.nirs.go.jp/research/jiscard/ (in Japanese)
Radiation exposure level
26
Radiation Exposure Level in Daily Life
a few mSv / flight
during large solar flare
(worst case)
Regulation of aircrew exposure
27
International Committee on Radiological Protection (ICRP) Aircrew exposure to cosmic-ray is recognized as an
occupational hazard in 1990
Each Country Issued the regulation laws for the annual dose limitation of aircrews
in Japan …
• Recommendation for the aircrew dose limitation (5 mSv/year) was issued in 2006
• It is desirable to forecast the aircrew doses during large solar flare using the latest
knowledge of the space weather research, and make adequate actions to reduce the
dose
Airline Companies • Estimate the annual doses for their aircrews using various calculation codes
JISCARD(Japan), CARI-6 (USA), EPCARD (Europe), PCAIRE (Canada)
• Do nothing for the second term due to the difficulty of forecasting doses
Conversion from flux to dose
30
Dose in human body ≠ Dose in the air
ICRP/ICRU adult reference
computational phantoms
Aircrew dose = Cosmic-ray Flux × Dose Conversion Coefficient
Dose Conversion Coefficient for ISO Irradiation
T. Sato et al. Phys. Med. Biol. 54, 1997, (2009), T. Sato et al. Phys. Med. Biol. 55, 2235, (2010)
• Radiological impact to human body by unit-flux irradiation
• Calculated based on the PHITS simulation
100
101
102
103
10410
0
101
102
103
104
Particle energy (MeV)
D
ose C
onvers
ion
Coeff
icie
nt
(pS
v c
m2)
Neutron
Proton
Photon*
*Photon data aretaken from ICRP116
Conversion from flux to dose
31
31
Atmospheric depth-dependence of doses from mono-energetic irradiations
• Flight altitudes: Protons above a few 100 MeV can contribute
• Sea level: Only GeV-order protons can contribute
Aircrew dose = Cosmic-ray Flux × Dose Conversion Coefficient
0 500 1000
10−2
100
102
104
Atmospheric Depth (g/cm2)
Dose (
pS
v)
100 MeV
300 MeV500 MeV1 GeV
3 GeV10 GeV
Flight
Altitude
Sea Level Proton
Incidence
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